The present invention relates to a semiconductor laser diode having a laser active semiconductor layer, a lesser doped semiconductor layer on the laser-active layer, a first more highly doped semiconductor layer on the lesser doped layer, a metal electrode layer on the highly doped semiconductor layer, and an additional semiconductor layer and additional electrode on the opposite side of the laser active layer.
Semiconductor strip laser diodes are known from the prior art in which a region is designed in a semiconductor body with a predetermined layer sequence consisting of n and p conductive semiconductor material in such manner that the amplification of coherent radiation corresponding to a laser diode practically occurs only within this region. The object of such a strip shape in a semiconductor strip laser diode is to suppress the transversal modes occurring with respect to directions other than the desired propagation direction of the generated laser beam and/or to confine the current between the electrodes of the semiconductor laser diode through the semiconductor body which is too widely spread in a lateral direction with respect to this desired beam direction.
Such semiconductor strip layer diodes, i.e. semiconductor laser diodes with a laser-active region forming the resonant cavity means for generation of laser radiation and which are designed only in a strip-like and narrowly limited lateral fashion, have been until now constructed such that a region has been generated with the assistance of expensive proton implantation, or that, in accordance with an earlier state of development, blocking pn junctions have been provided in the semiconductor body. Other structural types for such a laser diode are the so-called buried laser manufactured with the assistance of a double epitaxy with a buried laser-active layer or the channeled substrate planar laser in which, due to its structure, essentially only a control of the formation of the oscillation modes is achieved.